Green Sea Turtle

Despite an overall declining trend globally, green turtle population growth rates are variable among nesting populations and regions. The Hawaiian green turtle population is actually increasing in abundance and has increased 53% over the last 25 years. Low levels of green turtle nesting also occur in Guam, American Samoa, the Northern Mariana Islands, and other U.S. island territories. Information on population trends for green turtles in the region other than the Hawaiian stock is limited.

If you see sea turtles out basking (sleeping) on the beach or in the water while snorkeling, admire them from a reasonable distance of 10 feet (3 meters).

Please do not attempt to touch, feed or harass sea turtles.

Natural History

Green turtles are found throughout the world, occurring primarily in tropical, and to a lesser extent, subtropical waters. The Hawaiian green turtle is genetically distinct from the other green sea turtle populations, nesting primarily in the French Frigate Shoals of the Northwestern Hawaiian Islands and feeding in the coastal areas of the main Hawaiian Islands. This species was in a steep decline as of the 1970s because of direct harvest of both turtles and eggs by humans. The population has grown steadily over the last thirty years after protection began in 1978. Greens are the most common species of sea turtle found in Hawaiian waters.

Physical Description

A typical adult green turtle has a carapace length of 40 inches and can weigh from 200-500 lbs.

Green turtles exhibit counter-shading with a carapace (shell) that can range from olive brown to black in color and a much lighter yellow plastron (underside).

Green turtles have five vertebral scutes running down the middle of their shell and four costal scutes on each side. (Unlike the hawksbill turtle which has the same number of scutes, the scutes of the green turtle do not overlap).

Another distinguishing characteristic of this species is their two large prefrontal scales located between the eyes.

Diet

Adults primarily eat algae. Over 275 different species of seaweed have been found in the stomachs of Hawaiian green turtles. In order to deal with this diet of roughage, green turtles have microflora living in their large intestine that help breakdown the cellulose that is otherwise undigestible. Other food items they consume in lesser amounts include jellyfish, salps, mollusks, sponges, and tubeworms. East Pacific green turtles tend to eat more animal prey than other populations.

Lifespan

The lifespan for sea turtles in generally unknown but for green turtles is thought to be around 60-70 years.

Reproduction

Photo: Mating Hawaiian green sea turtles. Dr. Malia Rivera

Green turtles become sexually mature at 25-35 years, and some may be as old as 40 before being able to reproduce.

The length of reproductivity has been estimated to range from 17 to 23 years.

They return to nesting beaches to lay eggs every two to three years and will deposit three to six clutches per nesting season with an average of twelve days in between. Each clutch consists of about 100 eggs that will incubate for 60 days.

Distribution

Photo: Hawaiian green sea turtle hatchlings emerge from a nest on Tern Island in the French Frigate Shoals.

More than 90% of the Hawaiian population of green turtles nests at French Frigate Shoals in the Northwestern Hawaiian Islands. They migrate to feed mainly in the coastal areas of the Main Hawaiian Islands. Limited nesting locations and important coastal foraging areas for green turtles are found throughout the Pacific islands.

Local Cultural Significance

Photo: Hawaiian green sea turtle at Lanikaea beach

Historically, green turtles have played a large role in Polynesian and Micronesian cultures. In addition to being used as a food source, native peoples all over the Pacific utilized all parts of the turtle making tools and jewelry out of the bones, and containers and utensils out of the carapace. Turtle fat was sometimes used for medicinal purposes to treat burns and other skin disorders. Turtles were often considered the property of the tribal chief and their utilization was regulated by some form of island council.

In the Hawaiian Islands, there were families that considered the green turtle a personal family deity or aumakua, not to be eaten or harmed. One legendary example is the story from the Big Island of Hawaii of the turtle named Kauila. She was believed to be able to change at will into human form to watch over the village children playing near the shore. Artistic elements of green turtles have also been featured prominently in some cultures of the region, such as petroglyphs and tattoo designs.

Potential Threats

Disease - Disease is considered the primary threat to green turtles in Hawaii. Fibropapillomatosiscauses tumor growth on the exposed soft tissue including flippers, head, and neck areas. While the tumors do not appear to be accompanied by any other symptoms or negative effects, their location could be detrimental to the survival of an individual. For example, if a tumor obstructs a turtle's mouth or eyes enough, it may starve due to inability to locate and/or ingest food. Tumors around the eyes may also impair vision so that a turtle's ability to avoid predators is reduced.

Harvest - In a American Samoa, Guam and the Commonwealth of the Marianas Islands, direct harvest remains a serious threat to green turtle populations. Hawaiian green turtles have been successfully protected from these threats for over 25 years and their population growth is evidence of the success of such protection.

On February 16, 2012, NOAA Fisheries received a petition from the Association of Hawaiian Civic Clubs to classify the green sea turtle (Chelonia mydas) in Hawaii as a distinct population segment (DPS) and delist this DPS under the ESA.

On August 1, 2012, we made a positive 90-day finding (77 FR 45571), determining that the petitioned action may be warranted.

On March 23, 2015, NOAA Fisheries issued a 12-month finding and proposed rule to remove the current range-wide listing of the green sea turtle and, in its place, list eight DPSs as threatened and three DPSs as endangered (80 FR 15271). We then solicited comments on the proposal and held public hearings.

On April 6, 2016, we issued a final rule that removes the current range-wide listing of the green sea turtle and instead lists eight DPSs as threatened and three DPSs as endangered (final rule). Although we find that the Hawaiian green turtle population (referred to in the final rule as the Central North Pacific population) does constitute a DPS, we do not find that removing this population from the ESA is warranted. All green sea turtles in the Pacific Islands Region are protected by the ESA and remain protected under the final rule.